1. Field of the Invention
The present invention relates to industrial soldering equipment. More particularly, the present invention relates to a thermode solder blade for soldering small components in industrial soldering equipment.
2. The Prior Art
Conventional soldering systems, such as are used to solder components to printed circuit boards in electronic circuit production environments, have attained widespread use. These systems generally employ an electrically-driven hot bar solder head which is heated to a soldering temperature, such as 700.degree. F. In more complex systems, automatic positioning equipment is used to position the solder head with respect to components to be soldered.
In some automatic soldering applications, the soldering of small component leads is required. These leads may have tolerances of only a few thousandths of an inch. Accurate positioning and tolerance of the soldering head is plainly critical in such applications.
A typical prior art thermode soldering blade is disclosed in U.S. Pat. No. 5,010,227 to Todd. The prior art thermode disclosed in this patent includes a heat conducting body comprising a thin flat elongated member composed of a thermally conductive electrically insulative material. The body is provided with a bottom edge having a substantially flat surface throughout its entire longitudinal length for transferring uniformly thermal energy to the solder material.
A pair of first and second heating elements are disposed on opposite sides of the flat body and are separated from the flat plate by a pair of first and second elongated spacing members. The spacing members are used to electrically isolate the heating elements from the body but to permit heat flow from the heating elements to the body. The heating elements are covered by a pair of first and second heat-confining elongated members for directing the thermal energy generated by the heating elements toward the body.
While the thermode soldering blade disclosed and claimed in this prior art patent is satisfactory for use in many soldering applications, it has several drawbacks which severely limit or prohibit is use in certain applications. The heat-confining elongated members are subject to thermal fatigue and limit the useful life of the thermode.
In addition, while not stated in the patent, the heating elements in actual thermodes made by the assignee of the U.S. Pat. No. 5,010,227 patent all have electrical resistances on the order of less than 4 ohms. The prior art thermodes are designed to be driven by a low-voltage, high-current power supply, sold for use with the soldering system with which the prior-art thermodes are used. This arrangement requires heavy power supply cables which in turn cause positioning problems when attempting to employ precision positioning apparatus in a soldering system.
Another drawback of prior-art thermodes solder blades is the difficulty in designing a blade which can be used for soldering tasks in which the soldering blade encounters obstacles such as components mounted on the circuit board where soldering is to take place. Prior-art thermodes solder blades, such as the one disclosed in U.S. Pat. No. 5,010,227 cannot be formed into custom shapes. The process used to form the heating element requires a flat surface and must cover the entire soldering contact surface uniformly in order to avoid hot spots which would otherwise result in areas where the heating element would be thinned over a non-uniform surface.
It is therefore an object of the present invention to provide a thermode solder blade which overcomes the problems of the prior art.
It is a further object of the present invention to provide a thermode solder blade which may be more easily used in connection with precision positioning equipment.
It is yet another object of the present invention to provide a thermode solder blade which can be formed into custom shapes for soldering on surfaces with obstructions such as mounted components.